Electric vapor lamp apparatus and method of operation



Aug. 6, 1946. H. K. BOURNE v I ,2

I ELECTRIC VAPOR LAMP APPARATUS AND METHOD OF OPERATION Filed Aug. 25, 1944 f/WE/vm'z- HARRY KBUUR/Vf H5 ATTORNEY Patented Aug. 6, 1946 ELECTRIC VAPOR LAMP APPARATUS AND METHOD OF OPERATION Harry K. Bourne, Rugby, England, assignor to General Electric Com New York pany, a corporation of Application August 25, 1944, Serial No. 551,184

In Great Britain January 2, 1943 6 Claims. (01. 315-118) This invention relates to electric discharge A lamps generally, and more particularly to equipment for and methods of operating such lamps. It is frequently desired to reduce periodically the light output from high pressure mercury vapor lamps of the compact source type while enabling maximum light output to be immediately available. In order that these conditions may apply, it is essential that, during the periods ofreduced light output, i. e. of reduced power input, the discharge in the lamp should'be maintained or simmered. To do this, it is necessary to provide means for avoiding loss of heat from the envelope or for supplementing the'heating of the envelope to avoid too great a reduction of the vapor pressure within the envelope.

An object of the present invention is to provide a simple means for enabling a lamp of the kind set forth to beoperated under simmering conditions.

The invention consists in providing a heat conserving jacket between which and the lamp relative movement is effected during the change-over from maximum light output to simmering conditions, the. jacket enclosing the lamp and shielding it both thermally and optically during the time that it is operated under simmering conditions.

The heat conserving jacket thus serves, in addition, as an optical shutter, and is arranged to surround the lamp and substantially com-' pletely enclose it during simmering conditions. When moved relative to the lamp to permit maximum light emission therefrom, this movement takes place simultaneously with the operation of switching means for eifecting the removal of series resistance or inductance from the lamp circuit, whereby to increase the operating current through the lamp and enable the increased light output to be available. When the relative movement of lamp and jacket is reversed, the

resistance or inductance is re-inserted in the lamp circuit.

In one convenient embodiment, the heat conserving jacket is constituted as part of a reflector utilized for forming into a beam the light emitted from the lamp. Then, during the periods when the lamp is to be operated under simmering conditions and no light emission is desired, the lamp is retracted into the jacket; whilst when light emission is desired, the lamp is ejected from the jacket into a position within the reflector at which the source of light is situated at the focal point of the reflector. In one arrangement the heat conserving jacket projects the rear of a reflector 4.

position.

axially from the rear of the reflector, which may be of parabolic shape, and the lamp is held in a carriage slidable within the heat conserving jacket, a cap being arranged on the carriage to co-operate with the aperture in the reflector leading to the jacket. Thus when the lamp is retracted into the jacket, the cap covers the aperture and completely prevents light emission, while at the same time completing-the enclosure of the lamp in the jacket- When the lamp is ejected from the jacket it moves into a position in which the source of light is located at the focus of the reflector, the cap moving with the lamp and serving to preventthe emissionof direct rays from the lamp. r

To enable the invention to be more readily understood reference is now directed to the accompanying drawing which shows somewhat diagrammatically and in section an arrangement according to the invention.

Referring to the drawing the discharge lamp l is mounted in a suitable holder 2 forming part of a carriage movable with relation to a heat conserving jacket 3 which projects axially from The jacket 3 is provided with suitable lagging 5.

The jacket 3 is closed at its right-hand end by a fixed plug 6 having a central aperture in which slides tube 1 forming part of the carriage and containing the leads 8 which convey operating potential to the lamp I from a source of potential H, II through an inductance (choke coil) 12. In the drawing the carriage is shown in the position in which the lamp is ejected from the heat conserving jacket 3 into a position in which the light source is located, preferably at the focus of the reflector 4 which may be of parabolic shape. The position of the carriage is limited by an adjustable stop 9 fixed to the tube 1 which abuts against the plug 5. The carriage is also provided with a cap 09 which in the retracted position covers the otherwise open end of the heat conserving jacket 3 and limits the extent of movement of the carriage in the retracted In the position indicated the cap I!) also serves to prevent the emission of direct rays from the lamp I.

Switching means are provided whereby in the ejected position illustrated the power input to the lamp is increased, while in the retracted position the power input is diminished causing the lamp to simmer. Thi may be effected by inserting into the circuit With the lamp additional series resistance or inductance I3. The added inductance or resistance may be inserted autotained under simmering conditions by the provision of the heat conserving jacket which prevents cooling of the lamp and maintains the mercury vapor pressure within the :envelope thereof.

If desired; the retraction of the lamp into the. heat conserving jacket may be effected electromagnetically by making the carriage form the armature of an electromagnet energized by suitable switching means operated from a point remote from the lamp. This switchin means may then be arranged simultaneously to insert the additional series inductance or resistance simultaneously with the retraction of the lamp carriageinto the jacket.

Preferably the lamp is constructed in the manner disclosed in the British Patent No. 550,581 since the construction enables all the necessary supply conductors for the lamp to be connected thereto at the end of the lamp which is at all times within the jacket.

The arrangement shown may be utilized as a means for providing an intermittent beam of light for signalling purposes.

What I claim as new and desire to secure by Letters Patent of the United States is:

I. In combination, a high pressure mercury vapor lamp of the compact source type, a supporting and positioning fitting comprising a heat conserving jacket, a circuit for supplying power to said lamp, a carriage for supporting the lamp and movable with relation tothe jacket so that when the carriage is retracted into the jacket the lampv is thermally and optically shielded, and means simultaneously operated by the movement of the carriage for reducing the power input to the lamp when the carriage is retracted into the jacket, to an extent such that the lamp is operated under simmering conditions when shielded by the jacket and full light output from the lamp is immediately available when the power input is increased upon the carriage being ejected from the jacket.

2'. The invention as set forth in claim 1, in

4 which the carriage is provided with a cap which, in the retracted position of the carriage, covers the otherwise open end of the jacket and completes the optical and thermal shielding of the lamp.

3. The invention as set forth in claim 1, in which a reflector is provided and in which the carriage is provided with a cap which, in the retracted position of the carriage, covers the otherwise open end of the jacket and completes the optical and thermal shieldin of the lamp, and in which the jacket projects axially from the rear of said reflector which is adapted to direct the light from the lampwhen ejected from the jacket, the cap preventing the emission of direct rays from the lamp in the ejected position and covering the aperture in the reflector when the carriage is retracted into the jacket.

4. The combination of a high pressure mercury vapor electric discharge lamp of the compact source type, supporting and positioning structure comprising a fitting embodying a, heat conserving jacket and a carriage retractable thereinto and serving to support and selectively position the lamp in either a substantially ejected light emittin position or in a position substantially enclosed by said jacket, and means actuated by said carriage for connecting ahigh power source to said lamp when in its ejected position and a lower power source to said lamp when in its retracted position.

5. The method of operating a high pressure metal vapor electric discharge device which comprises alternately applying relatively high and low power across the terminals thereof, and enclosing the device in a thermal insulating jacket only during the periods of operation at loW power.

(-7. In combination, a high pressure mercury vapor lamp of a compact source type, a supporting and positioning structure for said lamp comprising a heat conserving jacket, a carriage for supporting said lamp and movable with relation to the jacket to eject said lamp from the jacket or retract it thereinto so that when retracted into the jacket the lamp is thermally and optically shielded thereby, a source of high power, a source of low power, and means responsive to the position of said carriage for selectively connecting the high power source to said; lamp in its ejected position and the low power source to said lamp in its retracted position.

HARRY K. BOURNE. 

